Differential Regulation of p53 function by Lysine Acetylation

描述（申请人提供）：应激诱导的p53 c端赖氨酸乙酰化在p53的活性中起重要作用，p53是一种调节细胞周期阻滞、衰老或凋亡的转录因子。该项目的长期目标是寻求对调节肿瘤抑制因子p53的分子相互作用的机制理解。虽然已经报道了其c端尾部的多个乙酰化位点，但这些赖氨酸残基的单独或联合乙酰化对p53活性的具体影响仍然难以捉摸。对p53功能的初步分析表明，乙酰化诱导的p53激活对DMA损伤的反应参与了共激活剂的募集。本研究表明，p53募集共激活因子CBP （CREB结合蛋白）需要CBP的保守溴域与p53在乙酰化Iys382位点的关联：这是一种特定的分子相互作用，对于p53诱导的细胞周期蛋白依赖性激酶抑制剂p21的转录激活至关重要，参与G1细胞周期阻滞。我们假设p53 c末端残基的不同修饰，包括赖氨酸乙酰化和泛素化，以及丝氨酸磷酸化，在不同条件下对细胞中p53功能有不同的影响。提出了一个多方面的方法来解决p53转录激活的机制基础，重点是c端翻译后修饰在p53激活中的作用。为了了解p53调控的复杂分子机制，我建议研究涉及其c端赖氨酸的乙酰化动力学和p53的分子相互作用。为了实现这一目标，提出了三个具体目标：(1)研究正常和肿瘤细胞系中p53功能中c端赖氨酸乙酰化的动力学；(2)阐明共激活因子p300和CBP在利用CHIP和sirna调控p53中的不同作用；(3)利用新开发的CBP bromodomain结合小分子抑制剂在细胞生长停滞和凋亡之间调节p53活性。新提出的研究结果有望增强我们对p53功能中c端修饰的分子基础的理解。鉴于p53在癌症中的核心作用，这些研究将对人类肿瘤的预后和治疗具有重要意义。

DESCRIPTION (provided by applicant): Stress-induced C-terminal lysine acetylation of p53 plays an important role in the activity of p53 as a transcription factor that regulates cell cycle arrest, senescence or apoptosis. The long-term goal of this Project is to seek mechanistic understanding of the molecular interactions that regulate the tumor suppressor p53. While multiple acetylation sites in its C-terminal tail have been reported, specific effects of individual or combined acetylation of these lysine residues on p53 activity remain elusive. Preliminary data is presented involving the analysis of p53 function that acetylation-induced p53 activation in response to DMA damage is involved in co-activator recruitment. This study revealed that p53 recruitment of the co-activator CBP (CREB binding protein) requires association of the conserved bromodomain of CBP with p53 at acetylated Iys382: a specific molecular interaction that is essential for p53-induced transcriptional activation of the cyclin- dependent kinase inhibitor p21, involved in G1 cell cycle arrest. We hypothesize that distinct modifications of p53 C-terminal residues, including lysine acetylation and ubiquitination, as well as serine phosphorylation, have differential effects on p53 functions in cells under different conditions. A multifaceted approach is proposed to address mechanistic underpinnings of p53 transcriptional activation with the emphasis on the role of C-terminal post-translational modifications in p53 activation. To understand the complex molecular mechanisms underlying p53 regulation, I propose to investigate the dynamics of acetylation and molecular interactions of p53 involving its C-terminal lysines. Three specific aims are proposed to achieve this goal: (1) to investigate the kinetics of acetylation of the C-terminal lysines in p53 function in normal and tumor cell lines; (2) to elucidate the differential roles of the co-activators p300 and CBP in p53 regulation using CHIP and siRNAs; and (3) to modulate p53 activity between cell growth arrest and apoptosis using the newly developed CBP Bromodomain-binding small molecule inhibitors. The emerging results from the proposed studies are expected to enhance our understanding of the molecular basis of C-terminal modifications in p53 function. Given the central role of p53 in cancer, these studies will have important implications for the prognosis and treatment of human tumors.